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I have a small mechanical room in the basement where my oil boiler is located. I've been told that it's a small room and I need to get outside air in for better efficiency, etc. I've installed a vent to the through to the outside wall and placed the vent approx. 12 inches from the floor near the boiler.

Question: Is there a louvered vent cap (similar to a dryer vent only allowing the air to flow in reverse) that would keep the vent closed when air is not needed and open when the furnace turns on and air is need? Reason being when I place my hand in front of the vent outside I can feel all my nice (and expensive) air conditioned air escaping. Anything I can do?